The need for active capability for non-traditional applications and its concomitant benefits are well-established. Although the event-based technique for monitoring conditions (leading to the integrated architecture) is the most versatile of all the techniques, from a practical viewpoint there is a need for enhancing pre-existing non-active DBMSs to support active capability. The set of techniques that can be used for providing this add-on active capability (leading to the layered architecture) imposes limitations on the active capability that can be supported. Insights into the details of techniques as well as their impact on the architecture entails a better design that meets the active database objectives. This paper identifies a repertoire of techniques for condition monitoring and discusses their suitability to different architectures. This paper argues that from a pragmatic viewpoint, both layered and integrated approaches to support active capability need to be pursued. Then it ...

this paper is to refine this definition somewhat, adapting it to the purposes of the research community in computer science. Accordingly, we shall attempt to provide a reasonable definition of or, rather, criteria for folk theorems, followed by a detailed example illustrating the ideas. The latter endeavor might take one of two possible forms. We could take a piece of folklore and show that it is a theorem, or take a theorem and show that it is folklore. As an example of the first form we could have shown that the statement P NP, which is folklore, is also a theorem. However, since we have resolved to introduce no new technical material in this paper, and moreover, since researchers in our community seem to be less familiar with folklore than with theorems, Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission

ion : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 10 2.2.3 Interface and Code Sharing : : : : : : : : : : : : : : : : : : : : : : : : : : 10 2.2.4 Polymorphism : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 11 2.2.5 Design Sharing : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 11 2.2.6 Summary : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 12 3 Related Work : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 13 3.1 Survey of File Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 13 3.1.1 Record File Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 13 3.1.2 Byte-Stream File Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : 14 3.1.3 Object Storage Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : : 15 3.1.4 Distributed File Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : : 18 3.1.5 Summary : : : : :...